An aquarium is not just a glass box with water, but an entire ecosystem where every detail plays its role. One of the key elements ensuring the cleanliness and health of this system is the filter. There are many models on the market today, from simple internal to complex external systems. In this article, I will break down the main types of aquarium filters, their pros and cons, so you can choose the one that is perfect for your underwater world.

Why is a filter so important?

A filter in an aquarium performs three main tasks: mechanical cleaning (removal of debris), biological filtration (decomposition of waste due to bacteria) and sometimes chemical cleaning (removal of toxins with the help of special fillers). Without it, the water will quickly become turbid, and the inhabitants of the aquarium will begin to suffer from the accumulation of ammonia and nitrates. So the choice of filter - it is not just a matter of aesthetics, and care about the health of fish, plants and even shrimp, if you have them.

Types of aquarium filters

Let's look at the main types of filters that you can meet in the shops.

1. Internal filters

This is the simplest and most affordable option. These filters are mounted inside the aquarium, usually with suction cups, and run on electricity or air (in the case of aerlift models).

• Pros: inexpensive, easy to install, suitable for small aquariums (up to 50-100 litres).
• Disadvantages: They take up space inside the aquarium, do not always cope with heavy pollution and require frequent cleaning.
• Who is suitable for: beginner aquarists or owners of small aquariums with unpretentious fish like guppies or neon.

An example of a popular model is the Tetra IN Plus or Aquael FAN. They are compact and cope well with basic tasks.

2. External (canister) filters

These filters are mounted on the outside of the aquarium and the water enters through hoses. Inside there are usually several compartments with different fillers: sponges, ceramic rings, charcoal.

• Pros: powerful, provide excellent filtration, do not take up space in the aquarium, suitable for large volumes (from 100 litres and above).
• Minuses: high price, more difficult to install and maintain, can be noisy if not set up correctly.
• Suitable for: Those who keep large fish (e.g. cichlids or goldfish) or aquariums with a large number of inhabitants.

A good example is the Eheim Classic or Fluval FX. These are real workhorses for serious aquariums.

3: Hang On Back (HOB) filters (HOB - Hang On Back)

These filters are suspended on the wall of the aquarium, with part of the unit outside and the water intake from the inside.

• Pros: compact, easy to maintain, good water circulation.
• Cons: not suitable for very large aquariums (over 200 litres), can make noise from falling water.
• Suitable for: owners of medium-sized aquariums (50-150 litres) who want a balanced solution.

Popular models are Aquaclear or Seachem Tidal. They are convenient and efficient for most standard aquariums.

4. Bottom filters

This type of filtration is based on passing water through the soil, which itself becomes the filter media. Usually used with a pump or airlift.

• Pros: cheap, suitable for aquariums with plants, as it improves water circulation in the ground.
• Cons: difficult to clean, ineffective for heavy pollution, requires proper adjustment.
• Who is suitable for: fans of planted aquariums with minimal bioburden.

Used less often, but in niche cases can be useful.

5. Sampas

Complex systems, most often used in large aquariums or professional installations. It is a tank under the aquarium where the water goes through several filtration stages.

• Pros: maximum efficiency, can be customised to suit any needs.
• Cons: expensive, requires space and knowledge for installation.
• Who is suitable for: professionals or enthusiasts with aquariums from 300 litres.

How to choose a filter?

When choosing a filter, it is important to consider several factors:

• The volume of the aquarium: the filter should pump 3-5 volumes of water per hour. For example, for 100 litres you need a filter with a capacity of 300-500 litres per hour.
• Type of inhabitants: for goldfish or discus you need a powerful filter, and for shrimp something softer will do.
• Budget: internal filters cost from $ 5, and good external filters can cost $ 100-200.
• Noise level: if the aquarium is in the bedroom, choose models with minimal noise.

Personal experience

I have a 60-litre aquarium at home with neon and plants. At first I used an Aquael internal filter, but then I switched to an Aquaclear mounted filter. The difference is enormous: the water is crystal clear and the filter needs to be cleaned less often. For a large aquarium with cichlids (200 litres) I would definitely take an external filter, for example, Eheim - it is reliable and does not fail.

Popular aquarium filters

Today, the popularity of aquarium filter models is determined by their efficiency, ease of use and adaptability to different aquarium volumes. Based on the latest aquarium trends and user reviews, here are a few models that stand out:

1. Tetra EX Plus (e.g. EX 600 Plus or EX 1200 Plus)

External canister filters from Tetra remain among the most sought-after due to their reliability, quiet operation and multi-stage cleaning (mechanical, biological and chemical). They are suitable for aquariums from 60 to 500 litres, depending on the model, and are appreciated for their ease of maintenance.

2. Eheim Classic (e.g. Classic 250 or 350)

The legendary line of external filters from Eheim continues to be popular with experienced aquarists. These models are characterised by their durability, quietness and high performance (440 to 620 litres per hour). They are ideal for medium to large aquariums (100-350 litres).

3. Aquael FAN (e.g. FAN 1 Plus or FAN 3 Plus)

Internal filters from the Polish brand Aquael are a frequent choice for small to medium-sized aquariums (60 to 250 litres). They are compact, affordable and provide good mechanical cleaning with aeration function, which makes them popular among beginners.

4. Fluval (e.g. Fluval 107 or 207)

Fluval's new generation of external filters attract attention due to their energy efficiency and clever filtration system. They are suitable for aquariums from 40 to 330 litres and are renowned for their quiet operation and easy replacement of filter media.

5. Aquael Versamax (e.g. Versamax 2)

Aquael's ‘waterfall’ type mounted filters are popular for small aquariums (20-200 litres). They are compact, do not take up space inside the tank and provide quality cleaning with oxygenation of water.

These models stand out due to their combination of performance, affordability, and positive user reviews. Trends for 2025 show a growing interest in energy efficient and quiet devices, as well as filters with modular systems that are easy to maintain.

Summary

Choosing an aquarium filter is a balance between your needs, budget, and the size of your aquarium. If you're just starting out, try an internal filter. For more serious projects, you should consider mounted or external models. Most importantly, don't skimp on quality, as the lives of your fish depend on the filter. What kind of filter do you use? Share your experience in the comments!